Shooting victim Mark Hummels, a partner at Phoenix law firm Osborn Maledon, "will not survive from the shooting," according to a statement from the firm. Hummels was shot in the neck and back.

Arthur Douglas Harmon, 70, whose body was found Thursday, appears to have died of a self-inflicted gunshot wound, Phoenix Police Sgt. Steve Martos said. Harmon's vehicle, a rented Kia Optima, also was found in the area.

"The body discovered in Mesa this morning has been identified as Arthur Douglas Harmon, the suspect in yesterday's shooting," Phoenix Police Sgt. Tommy Thompson said Thursday in a news release. Harmon had not been seen since fleeing the north-central Phoenix office complex where he was accused of shooting two men and another bystander following a pre-litigation meeting.

A landscaper at the shopping center found the body in some bushes before 8 a.m. MST, Mesa Police Sgt. Tony Landato said. A handgun also was discovered there.

Thompson said a possible motive for the shooting was that the meeting Harmon attended Wednesday morning "didn't go in favor of Mr. Harmon."

Wednesday's shooting victims were identified as:

Steven D. Singer, 48, chief executive officer at a call center and defendant in a lawsuit Harmon filed over furniture that Harmon's company, Reback Design, had refurbished. Singer, a husband and father of two, died from his injuries Wednesday.

Hummels, 43, a lawyer who represented Singer and served as Phoenix chapter president of the Federal Bar Association, suffered serious neck and back wounds. He had surgery Wednesday but is not expected to survive.

Nichole Hampton, 32, of Waddell, Ariz., who had gone outside to take pictures and was caught in gunfire near the building entrance. She is hospitalized with a wound to her hand.

Police said a shot was fired at a fourth victim who pursued the shooter from the scene, but the person was uninjured. Two other people also were taken from the scene to a hospital with unspecified medical issues related to the shooting.

"People are pretty devastated here," said Larry Hammond, a partner at Hummels' firm. "He is not going to survive. They are keeping him on life support for the good he can do for somebody else" via donor transplant.

Phoenix Mayor Greg Stanton, who spoke Thursday, said the city is grateful to the unidentified witness who chased after Harmon as he fled the office complex.

"He gave critical information to the police to help lead to where we are at this moment," Stanton said. "The private citizen risked his own life."

Wednesday's shooting occurred in the lobby of a broad, three-story building in the 7310 block of North 16th Street, just north of the Arizona Canal near Pointe Hilton Squaw Peak Resort.

The complex houses about a dozen companies doing business in real estate, insurance, medical care and other commerce. As shots rang through the courtyard, terrified workers reported locking doors and hiding until police swarmed the area.

"I looked out the window, in the back, and there were two bodies laying on the ground," said Rob Hayter, who works for a title company in the complex. Hayter said he heard five or six shots and saw a handful of bullet casings on the ground near the victims.

The shooting occurred as Congress was conducting hearings in Washington on laws proposed to address firearm violence - particularly mass killings. Among those advocating stricter gun laws was former Rep. Gabrielle Giffords, D-Ariz., wounded two years ago in a mass shooting near Tucson, Ariz., that left six dead and 13 others injured.

Thompson said the shooter targeted the two men.

According to Thompson and other sources, Harmon, Hummels and Singer had attended a mediation proceeding Wednesday morning at the law offices of DeConcini, McDonald, Yetwin & Lacy. Lisa Anne Davis, managing partner, said one of the firm's lawyers presided over the session as a court-appointed judge pro tem.

Mark Harrison, who works with Hummels at the firm of Osborn Maledon, said he was told the session was interrupted when Harmon announced he needed to go outside to his car.

When Harmon failed to return after a prolonged wait, Hummels, Singer and others assumed he was not coming back. They headed downstairs, and as they were leaving they were shot.

Hammond, a partner in Hummels' firm, said he is not familiar with the civil case Hummels was working on, and it is unclear what precipitated the shooting.

"No one has yet tried to piece together the history of that adversarial relationship," Hammond said.

Photographs show shattered glass sprayed across the building's courtyard.

Hampton, who was shot in the hand, is director of human resources at MD Home Health LLC, another business in the complex. In a phone interview from the hospital, Carol Hampton said her daughter got caught in the shooting frenzy.

"She was at the wrong place at the wrong time," Carol Hampton said.

Carol Hampton said Nichole Hampton was outside the building taking pictures for business purposes.

"She started walking to the lobby, and she saw four men come running out, saying, 'He's got a gun.' "

At that instant, Carol Hampton said, her daughter heard a shot and saw a window shatter. Nichole Hampton, initially unaware that she had been wounded, ran into the nearby office of a business known as Time to Rent.

Carol Hampton said an employee locked the door behind her.

"He was very nice," she said. "He took off his shirt and wrapped her hand up."

Carol Hampton said her daughter and others looked out a window to see the shooter's white vehicle screech out of the parking lot with its trunk open.

Carol Hampton said her daughter, who is married with two young children, was struck in the wrist, and two bones were broken.

"She has two metal plates and pins in her hand. She's pretty shook up," Carol Hampton said Wednesday. "But someone died in this, so we feel very lucky."

Police flooded the area, evacuating nearby offices and searching for a shooter while rescue crews tended to the wounded. Employees looked on, talking quietly among themselves, some crying.

According to court records, Singer had hired Harmon's firm almost a year ago to refurbish and move office furniture at the Santa Maria, Calif., offices of his call center, Fusion Contact Center LLC.

The contract was for $47,000, but a dispute erupted because not all of the work could be completed. The parties traded lengthy emails. In April, after receiving $30,000, court records say, Harmon filed suit.

As the legal case dragged on, court records say Harmon engaged in financial transactions with a son, Stefan Harmon. Legal filings allege that Arthur Harmon sold his home, valued at $100,000, to the son for $26,000, then borrowed $180,000 from another party using the home he no longer owned as collateral. The filings say that money then was loaned to Stefan Harmon.

Fusion countersued, alleging that Arthur Harmon, who had no legal counsel, was overpaid and fraudulently transferred property in connection with the litigation. The company sought a payment of $20,184 from Harmon to end the case. Harmon testified his savings totaled $17.

Mediation proceedings were set up to address continuing issues in the case.

After Wednesday's shooting, police went to the Harmon residence about 7 miles north. Martos of the Phoenix Police Department said a son refused to allow officers to enter until they obtained a search warrant. Once they did enter, they found no one there.

Police found an item that Harmon discarded, apparently after the shooting, not far from his house.

Court records indicate Harmon and his wife, Ivett Huska, have had financial problems previously. In 2005, faced with debts totaling $219,000, they sought bankruptcy protection. Lothar Goernitz, a trustee who became involved, said it was "a fairly mundane case."

Friends and business associates described Singer as a family man, mentor and innovator.

His company has offices in Scottsdale, Ariz., with sites in California and Nevada.

Singer spent most of his career in call-center management. Clients and co-workers who posted notes on Linkedin.com, a professional-networking website, praised him as a "thoughtful leader, adviser and mentor" and "top expert" in the field.

Jennifer Manning, a family friend, said Singer was a terrific father to two teenage sons and had an idyllic relationship with his wife, Lisa.

"It was like a love story," she said, sobbing. "They loved each other so much. ... It just hit so hard. There's shooting every day, and you don't expect it to be someone you know. He was such a wonderful man. He really, truthfully was."

Hummels graduated first in his law class at the University of Arizona, clerked under Arizona Supreme Court Justice Andrew Hurwitz and earned the highest score on the July 2004 state bar exam.

Hammond said Hummels clerked for Osborn Maledon while in law school, put in a stint as a state Supreme Court law clerk and returned to Osborn Maledon after graduation. Hummels was made a full partner two years ago.

A former newspaper reporter, Hummels specialized in business disputes, real-estate litigation and legal malpractice.

"The thing that always struck me about Mark was his humility, the way he approached things for a guy who had been so successful," Hammond said.